The present invention resides in an ignition resistant activated biregional fiber(s) having an inner region of a thermoplastic polymeric core and an activated outer sheath.
The present invention also resides in a method of making an activated biregional fiber(s) comprising an inner region of a thermoplastic polymeric core surrounded by an outer sheath region of an activated carbonaceous material. The activated biregional fiber is derived from an oxidation stabilized biregional fiber(s) which comprises an inner region of a thermoplastic polymeric core and an oxidation stabilized outer sheath region. In the method of the invention, the oxidation stabilized biregional fiber is subjected to an activating gas at a relatively high temperature and for a period of time sufficient to activate the outer sheath region.
The invention also relates to a method for the manufacture of an activated biregional fiber(s) derived from a biregional fiber(s) comprised of an inner region of a thermoplastic polymeric core and an outer region of a carbonaceous sheath. In the method of the invention, the biregional carbonaceous fiber is subjected to an activating gas at a relatively high temperature and for a period of time sufficient to activate the outer sheath region. The activated biregional fiber(s) has an inner region of a thermoplastic polymeric core and an outer sheath region of an activated carbonaceous material.
Oxidation stabilized biregional fiber(s) and their method of manufacture are known from U.S. Pat. No. 5,763,103 issued Jun. 9, 1998 to Francis P. McCullough, the subject matter of which is incorporated herein in its entirety. This patent discloses an oxidation stabilized biregional fiber(s) which is produced from a homogenous polymeric composition in which an outer sheath portion of the fiber is oxidation stabilized while the inner core of the fiber remains in a thermoplastic polymeric condition. The patent is a divisional of application Ser. No. 428,691, now U.S. Pat. No. 5,700,573 issued Dec. 23, 1997.
U.S. Pat. No. 5,700 573 issued Dec. 23, 1997 to Francis P. McCullough discloses a biregional carbonaceous fiber(s) which is produced from a homogenous polymeric composition in which an outer fiber portion of the polymeric material is oxidation stabilized and then carbonized to form a fiber having a thermoplastic inner core and a thermoset or carbonized outer sheath. The subject matter of this patent is incorporated herein in its entirety.
The term xe2x80x9cbiregional fiberxe2x80x9d or xe2x80x9cbiregional fibersxe2x80x9d used herein is generally applicable to fibers having an inner core of a thermoplastic polymeric composition and a surrounding outer sheath that can be oxidation stabilized or carbonized in accordance with the processes described in the patents to McCullough acknowledged and specifically referred to herein above. The broad definition for the oxidation stabilized biregional fiber and the biregional carbonaceous fiber is applicable as well to the biregional activated carbon fiber(s) of the invention in which the inner core also comprises a thermoplastic polymeric composition while the surrounding outer sheath, however, comprises an activated carbonaceous material.
The term xe2x80x9cactivatedxe2x80x9d used herein refers to a carbonaceous material having a greatly enhanced surface area. The material behaves similar to an xe2x80x9cactivated carbonxe2x80x9d material, which is characterized by having a high absorptivity for many gases, vapors and colloidal solids. See Hawley""s Condensed Chemical Dictionary, Eleventh Ed. More specifically, activated carbon that is known in the art is carbonized and activated throughout the particle or fiber whereas the activated biregional fiber(s) of the invention has high surface area and porosity in the sheath but is not activated or carbonized in the core. Accordingly, the activated fiber of the invention behaves similar to that of activated carbon, i.e. it is absorptive, but is much faster in kinetic rate since the fibers are much smaller than activated carbon granules and present more readily contactable distributed surface per unit weight. More importantly, the activated fiber(s) of the invention is very flexible and not brittle like activated carbon fibers of the art since the fiber of the invention is biregional having an inner core of the thermoplastic polymeric composition
All percentages given herein are in xe2x80x9cpercent by weightxe2x80x9d unless otherwise specified.
It is an object of the invention to provide A biregional fiber(s) in which the outer surface region of an oxidation stabilized or carbonized biregional fiber(s) is activated so as to provide a highly porous structure having an extremely large surface area of from about 50 m2/gm (square meters per gram) to greater than about 2000 m2/gm, depending on the diameter of the fiber.
It is an another object of the invention to provide a process of manufacture in which an oxidation stabilized biregional fiber(s) is activated on it outer region (sheath region) to form a fiber having an inner core region of a thermoplastic polymeric composition which is surrounded by an outer sheath region of activated carbonaceous material.
It is also within the ambit of the present invention to activate a biregional fiber(s) in which the outer region of the fiber has been partially or fully carbonized. Activation being accomplished under the same conditions as described in connection with the oxidation stabilized biregional fiber(s).
It is also within the scope of the invention to activate a biregional fiber comprising 2 or more co-extruded compatible polymeric compositions in which one thermoplastic polymeric composition is extruded as an inner core and another compatible polymeric composition is extruded so that it surrounds the core to form an outer sheath of the fiber. The biregional polymeric fiber is subsequently oxidation stabilized and activated or, optionally, carbonized and then activated.
It is also an object of the invention to form of a multiplicity of the activated biregional fibers into articles of manufacture in the form of a wool-like fluff, a generally planar non-woven sheet, web, felt or batting, a compression formed panel, a woven or knitted fabric, etc. In a preferred embodiment, the fibers are in the form of a felt that is particularly adapted for use in the storage of gases as, for example, in the storage of hydrogen for fuel cells. Another end use for the felt is in the separation of a mixture of gases.
Additionally, it is also within the scope of the invention to treat the activated fibers with any of the many activity enhancement agents know to those skilled in the art such as metal salts such as silver salts and other transition metal ion salts, halogens, organic compounds including quaternary salts, organosilicone compounds to enhance the activity of the activated biregional fibers of the invention.
Further objects of the invention, not specifically recited herein above, will become apparent from a reading of the detailed description of the invention.